Telephony, messaging and on-demand streaming services are examples for Point-to-Point (PTP) or unicast communication services. Broadcast and multicast services, on the other hand, are based on Point-To-Multipoint (PTM) communication. Using PTM communication, content (such as voice, text, graphics or multimedia data) is transmitted from typically a single source to multiple destinations. PTM services might for example be streaming services or file delivery services.
A multicast PTM service delivers content to users who have registered to a particular multicast group. Usually, a multicast group includes a plurality of users interested in a particular content, for example news in the field of sports, economics, politics, etc.
A broadcast PTM service of a broadcast-enabled network, for example a mobile network, broadcasts content data into a predetermined geographical area. The users do not need to register or join a group prior to receiving the content.
The 3GPP (3rd-Generation Partnership Project) has specified broadcast and multicast services for GSM (Global System for Mobile Communications) and UMTS (Universal Mobile Telecommunications System) networks, namely the Multimedia Broadcast and Multicast Service (MBMS) feature. The feature is documented for example in the 3GPP TS (Technical Specification) 23.246 and in the TS 26.346. MBMS adds a plurality of broadcast/multicast-related techniques to conventional GSM or UMTS networks. For performing these techniques, a functional entity is specified that controls the broadcast/multicast delivery of services, which is called the broadcast/multicast service centre (BM-SC).
Within MBMS, the BM-SC is responsible for providing and delivering broadcast/multicast services. The BM-SC serves as an entry point for content-delivery services, sets up and controls MBMS transport bearers, and can additionally be used to initiate MBMS transmissions. For example, the BM-SC may provide the service announcements that signal an upcoming multicast transmission to the user equipment (UE) being member of the related group. These announcements include all necessary information such as multicast service identifier, Internet Protocol (IP) multicast addresses, time of transmission, and media descriptions that a user equipment needs to join a multicast session.
Each broadcast/multicast service is related to a service area—the geographical area or zone, within which the content can be broadcasted or transmitted. The service area may comprise the whole PLMN (Public Land Mobile Network) of an MNO (Mobile Network Operator) or may even comprise several PLMNs, if agreed upon in a service level agreement. On the other hand, a service area may be configured to be as small as a single radio cell of a network. In general, a service area comprises a reasonable part of a PLMN.
Downstream of a PTM data source, each node in the network has a list of further downstream nodes to determine to which nodes it should forward MBMS content. Thus, a hierarchically organized content distribution tree is created with the base transceiver stations/Node B stations serving a single radio cell each and thus forming the leaves of the distribution tree.
A multicast service requires that the network knows the location of the group members registered for the service group. It is necessary to keep track of the movement of the users (inside the group service area, i.e. the service area for this particular group), even if the MBMS transmission bearer is idle, i.e. no content transmission is ongoing. Therefore a complex group management function is required, for example in the core network and the radio network of a mobile network, to be able to establish the transmission tree efficiently from a network resource point of view.
A broadcast service does not include any group management function, and therefore requires much less resources. For example, the MBMS broadcast mode only offers simple PTM transmission, i.e. the network does not keep track of the movements of the users before or during an MBMS transmission. The content is broadcasted into the broadcast service area, irrespective of locations of users which might be interested in the content. This means that the broadcast service area has to be configured as large as possible, and preferably comprises the whole broadcast-enabled network, at least for non-localized services, to ensure that the content can be received by interested users. This again leads to a waste of resources, as there might be cells or geographical areas where only very few users (or even none) are located which are interested in receiving the broadcasted content.
Accordingly, there is a need to provide an improved PTM transmission technique.